Hi, I've got a rather battered Issue 1 ZX81 that I'm considering restoring (I already have another fully-refurbed one I bought from Ebay)
It powers up OK, but some keys don't work - HJKL and NEWLINE.
I opened it up and checked the keyboard connectors and they look ok - no obvious breaks, so I'm not sure that getting a replacement keyboard would fix it.
Also If I connect a RAM pack to it (I know the RAM pack works) then it shows a blank screen. I've tried two different RAM packs with the same result.
Any ideas?
Issue 1 ZX81, some keys not working - keyboard looks ok, also RAM packs don't work
Re: Issue 1 ZX81, some keys not working - keyboard looks ok, also RAM packs don't work
You could test the keyboard issue by unplugging the keyboard and carefully shorting the wires that would be connected on the keyboard matrix by those keys and see if the "key presses" register. For the ram pack issue, clean the expansion connector and test the connections. A blank screen means the ram test is probably failing.Ravenger wrote: ↑Thu May 20, 2021 4:08 pm Hi, I've got a rather battered Issue 1 ZX81 that I'm considering restoring (I already have another fully-refurbed one I bought from Ebay)
It powers up OK, but some keys don't work - HJKL and NEWLINE.
I opened it up and checked the keyboard connectors and they look ok - no obvious breaks, so I'm not sure that getting a replacement keyboard would fix it.
Also If I connect a RAM pack to it (I know the RAM pack works) then it shows a blank screen. I've tried two different RAM packs with the same result.
Any ideas?
Re: Issue 1 ZX81, some keys not working - keyboard looks ok, also RAM packs don't work
HJKL NL is D7.
D7 and RAM CS lines are one near each other in the back connector. It surely is a coincidence but doble check nothing is wrong there..
Test it using a thin insulated wire connecting the keyboard contacts in the board socket from the large one to any one in the smaller one. You should see the characters appear in the screen. D7 and RAM CS lines are one near each other in the back connector. It surely is a coincidence but doble check nothing is wrong there..
Ernesto
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come
ZX80 USA, ZX81UK, ZX Spectrum, ZX Spectrum+, ZX Spectrum 128+ UK, ZX Spectrum +2/A, Sinclair QL, CZ1000, CZ1500, CZ2000, CZ1000Plus, CZ1500Plus, CZ Spectrum, CZ Spectrum Plus, TK83, TK85, TK90X, TK95. TS2068. And more to come